diff --git a/libsolidity/analysis/NameAndTypeResolver.cpp b/libsolidity/analysis/NameAndTypeResolver.cpp
index 260965ae3..47a9df1bd 100644
--- a/libsolidity/analysis/NameAndTypeResolver.cpp
+++ b/libsolidity/analysis/NameAndTypeResolver.cpp
@@ -264,22 +264,15 @@ vector<Declaration const*> NameAndTypeResolver::cleanedDeclarations(
 		solAssert(dynamic_cast<FunctionDefinition const*>(*it) || dynamic_cast<VariableDeclaration const*>(*it),
 			"Found overloading involving something not a function or a variable");
 
-		unique_ptr<FunctionType const> functionType {};
-
-		if (FunctionDefinition const* functionDefinition = dynamic_cast<FunctionDefinition const*>(*it))
-		{
-			functionType = unique_ptr<FunctionType const>(new FunctionType(*functionDefinition));
-			for (auto parameter: functionType->parameterTypes() + functionType->returnParameterTypes())
-				if (!parameter)
-					reportFatalDeclarationError(_identifier.location(), "Function type can not be used in this context");
-		}
-		else
-		{
-			VariableDeclaration const* variableDeclaration = dynamic_cast<VariableDeclaration const*>(*it);
-			functionType = unique_ptr<FunctionType const>(new FunctionType(*variableDeclaration));
-		}
+		shared_ptr<FunctionType const> functionType { (*it)->functionType(false) };
+		if (!functionType)
+			functionType = (*it)->functionType(true);
 		solAssert(functionType, "failed to determine the function type of the overloaded");
 
+		for (auto parameter: functionType->parameterTypes() + functionType->returnParameterTypes())
+			if (!parameter)
+				reportFatalDeclarationError(_identifier.location(), "Function type can not be used in this context");
+
 		if (uniqueFunctions.end() == find_if(
 			uniqueFunctions.begin(),
 			uniqueFunctions.end(),
diff --git a/libsolidity/ast/AST.cpp b/libsolidity/ast/AST.cpp
index 78d8949ca..ac92eaa32 100644
--- a/libsolidity/ast/AST.cpp
+++ b/libsolidity/ast/AST.cpp
@@ -274,6 +274,45 @@ TypeDeclarationAnnotation& EnumDefinition::annotation() const
 	return static_cast<TypeDeclarationAnnotation&>(*m_annotation);
 }
 
+shared_ptr<FunctionType const> FunctionDefinition::functionType(bool _internal) const
+{
+	if (_internal)
+	{
+		switch (visibility())
+		{
+		case Declaration::Visibility::Default:
+			solAssert(false, "visibility() should not return Default");
+		case Declaration::Visibility::Private:
+		case Declaration::Visibility::Internal:
+		case Declaration::Visibility::Public:
+			return make_shared<FunctionType const>(*this, _internal);
+		case Declaration::Visibility::External:
+			return {};
+		default:
+			solAssert(false, "visibility() should not return a Visibility");
+		}
+	}
+	else
+	{
+		switch (visibility())
+		{
+		case Declaration::Visibility::Default:
+			solAssert(false, "visibility() should not return Default");
+		case Declaration::Visibility::Private:
+		case Declaration::Visibility::Internal:
+			return {};
+		case Declaration::Visibility::Public:
+		case Declaration::Visibility::External:
+			return make_shared<FunctionType const>(*this, _internal);
+		default:
+			solAssert(false, "visibility() should not return a Visibility");
+		}
+	}
+
+	// To make the compiler happy
+	return {};
+}
+
 TypePointer FunctionDefinition::type() const
 {
 	return make_shared<FunctionType>(*this);
@@ -365,6 +404,28 @@ TypePointer VariableDeclaration::type() const
 	return annotation().type;
 }
 
+shared_ptr<FunctionType const> VariableDeclaration::functionType(bool _internal) const
+{
+	if (_internal)
+		return {};
+	switch (visibility())
+	{
+	case Declaration::Visibility::Default:
+		solAssert(false, "visibility() should not return Default");
+	case Declaration::Visibility::Private:
+	case Declaration::Visibility::Internal:
+		return {};
+	case Declaration::Visibility::Public:
+	case Declaration::Visibility::External:
+		return make_shared<FunctionType const>(*this);
+	default:
+		solAssert(false, "visibility() should not return a Visibility");
+	}
+
+	// To make the compiler happy
+	return {};
+}
+
 VariableDeclarationAnnotation& VariableDeclaration::annotation() const
 {
 	if (!m_annotation)
diff --git a/libsolidity/ast/AST.h b/libsolidity/ast/AST.h
index ab4be1eaf..088d68dbe 100644
--- a/libsolidity/ast/AST.h
+++ b/libsolidity/ast/AST.h
@@ -171,6 +171,10 @@ public:
 	/// This can only be called once types of variable declarations have already been resolved.
 	virtual TypePointer type() const = 0;
 
+	/// @param _internal false indicates external interface is concerned, true indicates internal interface is concerned.
+	/// @returns null when it is not accessible as a function.
+	virtual std::shared_ptr<FunctionType const> functionType(bool /*_internal*/) const { return {}; }
+
 protected:
 	virtual Visibility defaultVisibility() const { return Visibility::Public; }
 
@@ -581,6 +585,10 @@ public:
 
 	virtual TypePointer type() const override;
 
+	/// @param _internal false indicates external interface is concerned, true indicates internal interface is concerned.
+	/// @returns null when it is not accessible as a function.
+	virtual std::shared_ptr<FunctionType const> functionType(bool /*_internal*/) const override;
+
 	virtual FunctionDefinitionAnnotation& annotation() const override;
 
 private:
@@ -643,6 +651,10 @@ public:
 
 	virtual TypePointer type() const override;
 
+	/// @param _internal false indicates external interface is concerned, true indicates internal interface is concerned.
+	/// @returns null when it is not accessible as a function.
+	virtual std::shared_ptr<FunctionType const> functionType(bool /*_internal*/) const override;
+
 	virtual VariableDeclarationAnnotation& annotation() const override;
 
 protected: